Transgenic Trees
What are Transgenic Trees?
Transgenic trees are created through genetic engineering to contain a specific set of genes. Genes are added to, or taken out of, the tree's genome during the genetic engineering process using techniques such as recombinant DNA techniques and mutagenesis. Therefore, transgenic trees are also known as genetically engineered trees, or genetically modified trees. Genetic engineering incorporates the desired genes much faster than traditional selective breeding, or hybridization processes, which can take decades to fully incorporate traits from one tree into another.
Types of Transgenic Trees
Although transgenic trees have applications for several different industries, development is currently centred on modifying trees for the forestry industry. Researchers are in the process of creating transgenic trees which contain special traits for a wide variety of applications. Some of the traits include those that will allow for:
Learn more about Phytoremediation.
The aim of developing these transgenic trees is to increase the production of wood and wood products, which are important to the Canadian economy, while decreasing the environmental impact and conserving Canadian forests.
Transgenic trees are created by inserting a new gene, or a modified gene, into a tree cell. Inserting the new gene into a host tree cell is an important step in creating transgenic trees. However, the most time-intensive task involves identifying trees, plants, or other organisms that have a trait that scientists would like to incorporate into the host tree. Scientists then determine which method to use to insert the desired DNA sequence into the host tree.
Creating Pest-Resistant Trees
The bacterium Bacillus thuringiensis (B.t.) is the microorganism used by the Canadian Forest Service (CFS) to gain knowledge and refine strategies for the development of pest-resistant transgenic trees. Currently, a protein produced by this bacteria, known as Bt toxin, is widely used as a non-chemical insecticide. Working with other researchers, including those at the University of Ottawa, the CFS researchers are trying to identify the gene which codes for the production of this protein so they can then insert it into the genome of a host tree. They are also looking into developing a way to make the production of the protein in the host tree specific to environmental triggers, such as exposure to the pest. Isolating the Trait's Source Scientists first identify what controls the desired trait. For example, a particular protein might be responsible for disease-resistance. Once the trait is identified, the scientists can begin to look for the location of the gene that codes for the desired trait in the donor tree. Once this is done, the gene can be extracted from the donor tree and transferred into the host tree cell. Transferring the Trait
Working with other researchers, including those at the University of Ottawa, the CFS researchers are trying to identify the gene which codes for the production of this protein so they can then insert it into the genome of a host tree. They are also looking into developing a way to make the production of the protein in the host tree specific to environmental triggers, such as exposure to the pest.
Isolating the Trait's Source
Scientists first identify what controls the desired trait. For example, a particular protein might be responsible for disease-resistance. Once the trait is identified, the scientists can begin to look for the location of the gene that codes for the desired trait in the donor tree. Once this is done, the gene can be extracted from the donor tree and transferred into the host tree cell.
There are several biotechnology-derived techniques that can be used to transfer genes into the host tree cell. The four main methods used are outlined below. In all the cases, the gene needs to be physically inserted into the cell.
Method: Bacterial Vectors How does it work? This method uses naturally occurring soil bacteria to transport the genes into the host tree cell. Method: Micro-injection How does it work? A very small needle is used to inject the new gene into the host tree cell. Method: Electroporation How does it work? A lab technique that uses electric current to open the holes in cell membranes in order to allow foreign DNA molecules to enter the cell. Method: Microparticle Bombardment How does it work? The gene is attached to tiny "bullets" made of tungsten or other metal. The tiny particles are then literally "shot" through the plasma membrane into plant cells by a "gene gun."
Method: Bacterial Vectors How does it work? This method uses naturally occurring soil bacteria to transport the genes into the host tree cell.
Method: Micro-injection How does it work? A very small needle is used to inject the new gene into the host tree cell.
Method: Electroporation How does it work? A lab technique that uses electric current to open the holes in cell membranes in order to allow foreign DNA molecules to enter the cell.
Method: Microparticle Bombardment How does it work? The gene is attached to tiny "bullets" made of tungsten or other metal. The tiny particles are then literally "shot" through the plasma membrane into plant cells by a "gene gun."
Once the cell receives the modified genes, it is cultured, and grown into a mature tree. Researchers are also looking into cloning trees in order to be able to decrease the cost of manufacturing the transgenic trees.
Biotechnology has always been used to create new species of trees. Traditional forms of biotechnology, such as selective breeding and hybridization, were used for centuries to cross-breed plants and trees for desired traits. Modern forms of biotechnology, such as recombinant DNA techniques, are integral in the development of new transgenic trees. These techniques allow for quicker gene transfer than traditional methods. For example, cross-breeding a disease-susceptible tree with a disease-resistant tree can take many generations of tree breeding, and some scientists may not see results in their lifetime. Today, using recombinant DNA techniques, this can be accomplished much quicker.
Current Research Areas in Transgenic Trees
Before a transgenic tree can be created, researchers must first find the trees which have the most desirable traits. For example, if a researcher wanted to create a pest-resistant tree, they would have to find a tree or other organism which is already pest-resistant, in order to incorporate that gene into the non-pest-resistant tree. Current research areas include the creation of transgenic trees, and finding trees and other organisms which possess the desired traits to be transferred. The mapping of tree and plant genomes is one way researchers can look for genes responsible for specific traits. Mapping the genomes allows for the identification of species-specific traits, and their location within the organism's DNA. Later, transgenic trees can be created using the specific piece of DNA located through genome mapping.
Development and Transgenic Trees
Many scientists, and others, see the creation of transgenic trees as integral to creating a sustainable forestry industry. Transgenic trees that grow faster are being developed. Biotechnology, including tree engineering, may contribute to an increase in tree productivity per unit of land by providing tools to increase tree production, as well as by reducing dependency upon pesticides. Supporters of transgenic trees say this will mean that less forests will need to be cut down. Transgenic trees can also be used to clean-up environmental pollutants, becoming not only a component of a healthy environment but also a tool for creating one.
Ag-West Biotech Inc. Biotechnology in the Forest Industry Aids Production and Environmental Protection. The AGBIOTECH Infosource. Issue 31, November 1997.
Canadian Forest Service. Building a Better Tree. Accessed June 2002.
Canadian Forest Service. Environmental Impacts of Forest Biotechnology. Accessed June 2002.
Canadian Forest Service. Identification of Genetically Superior Trees and Genetic Diversity. Accessed May 2002.
Canadian Forest Service. Genetically Modified Trees. Accessed June 2002.
Lubick, Naomi. Explore!: Designing Trees. Scientific American. April 01, 2002.
University of Georgia. Warnell School of Forest Resources. Research Page: Engineering trees that can clean up. Accessed May 2002.